Telephone device



Se t. .P 1927 1.. DE FOREST TELEPHONE DEVICE I Filed April 28, 1923 3 Sheets-Sheet 1 IN VENTOR ATTORNEYS 1,642,363 p 13! 9 DE FOREST TELEI HONE DEVICE Filed April 28, 1923 3 Sheets-Sheet 2 so; & IN VENTOR 9J1 A TTORNE Y 3 Sept. 13, 1927.

1L. DE FOREST TELEPHONE DEVI-CE Filed April 28, 1923 INVENTOR ATTORNEY 3 Sheets-Sheet 3 Patented Sept.- 13, 1927.

name sr rEs tenses PATENT orator.

LEE DE EoREs'r, or NEW YORK, N. Y., Assxenon TO DIE EonEsr rnoNoEILM ooEroEA- TION, or NEW YORK, N. a, A coarorm'rron or DELAWARE.

TELEPHONE DEVICE.

'Application filed April 28, 1923. Serial No. 635,336.

This invention relates to telephone devices and more particularly to means for transforming electric tele' honic currents into sound waves to avoi the use of a diaphragm or any form of mechanical vibrating member. w

In general the method employed in accordance with my invention consists in employing a source of compressed air and expelling the same from a reservoir into a suitable horn or megaphone at the small end of which are located two highly charged and oppositely charged electrodes of any suitable form or construction, between which or past which the compressed airpasses on its way to the megaphone. The electrodes are employed whereby the stream of air is charged either positive or negative and therefore is attracted to or repelled from one or both of the electrodes, the. current flowing through the electrodes being controlled by and in accordance with sound waves.

The invention consists substantially in the construction, combination, location and relative arrangement of parts, together with the method employed in connection therewith,

all as will he more fully hereinafter set forth,

as shown in the accompanying drawings and finallypointed out in the appended claims.

Referring to the accompanying drawings:-

Fig. 1 is a diagrammatic illustration, partly in section, of a megaphone embodying my invention.

Fig. 2 is a sectional view taken on the line 22 of Fig. 1 and looking in the direction of the arrows.

Fig. 3 shows a modified arrangement of the electrical connection of the electrodes 40 employed in accordance with my invention.

Fig. 4: is a modified arrangement of electrodes embodying my invention.

Fig. 5 is a detailed view in side elevation showing a still further modified arrangement of electrodes in accordance with my 1nvention.

Figs. G'to 19. all show varying forms of electrodes and arrangements employed in accordance with my invention.

The same part is designated by. the same reference character wherever it occurs throughout the several views.

Referring to Fig. 1 of the drawings, refesignates an air reservoir erenre character 1 as WhlCh contains compressed air delivered thereto from the compressor? A pipe 2.

conducts the air from this reservoir to the i sound chamber '4 on the opposite side of which is a small orifice which opens into the horn or megaphone 5. The stream of air passing into the megaphone 5 passes between two sharp-edged electrodes 6Land 7, which are located close to each other leaving a narrow gap therebetween. This arrangement is more clearly shown in Fig. 2. Electrode 7 is connectetd to one terminal of a secondary winding of a telephone transformer 9, and the electrode 6 is connected through a battery or other source of E. M. F. 8 to the other terminal of the secondary winding 9. The telephonic currents which are to be transformed into sound waves are led into the amplifying audion 11, in the usual way, and the output circuit of this amplifier includes the primary winding 10 of the telephone transformer included in the electrodes 6. and 7, and by meansthereof the normal smooth flow of the air through a gap between such closely juxtaposed electrodes is more or less interrupted because the particles of air immediately adjoining the electrodes become electrically charged therefrom and therefore these particles .seek to travel transversely to the normal air flow and to reach the oppositely charged electrode, thus creating a friction or opposition to this normal flow of air.

Such turbulations or eddies in the air stream, if following each other with suflicient rapidity, produce sound waves in the air stream. It is obvious that these sound waves correspond to the telephonic E. M. Fs and therefore reproduceithe original sound which originally produced the telephonic currents.

it is not always essential that these electrodes 6 and 7 be directly exposed to the air, for they can in some cases be insulated, preferably by a thin coating of insulating material. In Fig. 3 I show the same'general arrangement but differing from the arrangement of Fig. 1 in that the electrodes 6 and 7 are included seriatim in the plate filament circuit of the audion amplifier 11.

In Fig. 4 Ishow still another arrangeno ment for producing the sound effects above described. In the arrangement shown here, the stream of air advancing from the reservoir 1 towards the horn 5 passes first 5 through a comb or series of grids 13 and 13' which are highly'charged from thetbattery or other suitable source of E. M. F. 14.

The other terminal of the current source 14 may be grounded as shown at 15, i. e. if a separate current source 8 is employed in connection with the electrodes 6 and 7. controlelectrodes 6 and 7 operate in the same way as described in connection with Fig. 1 for impeding more or less the normal smooth passage of air therebetween in accordance with the impressed telephonic E. M. Ffs delivered to the electrodes 6 and 7 from the transformer 9 and 10. If the air is first highly charged electrically, either positively or negatively, as is the case by employing the comb or grid device 13, l find that it is more readily controlled by the potentials impressed upon the electrodes. 6 and l. r

' Fig. 5 shows more clearly the preferred arrangement of combs or grids in the chamher l. In the form shown, the various teeth.

of the combs or grids are interpositioned relative to each other in the form of battery platesvor the like It will be understood, of course, that the electrodes 13 and 13 which support the teeth of the comb or grid structures are insulated from the chamber 4 if I a metallic chamber is employed. It will also be understood that the type of electrode structures 13 and 13 may also be em ployed for the electrodes 6 and 7 in place of the structure thereof shown in Fig. 2.

Instead of having the control electrodes 6 and 7 juxtaposed and close together they may be separated from each other and in.

separate enclosing chambers, as shown in Fig. 6, wherein the air from the reservoir 1 passing through the tube 2 enters the first chamber 4 which is partitioned by means oi. the comb or grid 60. The air is highly charged by coming in contact with this grid.

and then passes into the chamber 4* which is likewise partitioned by means of the grid or comb 70. The air passes through this grid 70 into the mouth of the megaphone, which is not shown in this figure.

The foregoing arrangement is partially modified in the arrangement 'shown'in Fig. 7, wherein the comb electrodes and (or if desired, the electrodes 6 and 7), are

connected to the ends of the secondary 9 of the tele hone transformer, with the high potentia battery 8 connected or not conto Cnected, as desired, in this line in series with the transformer secondary.

InFig. 8 I show a modified arrangement of the control or charging electrode 6 or 60, as desired. In this case a disc is employed which is pierced -to form a large The neaaeea electrode is in the form of a number of parallel wires stretched very closeto eachother. The arrangement of Fig; 9 obviously is preferable for use as a charging electrode as distinguished from the control elect-rode.

By reason of the foregoing arrangements all particles of air must pass in close proximity to a portion of thecharged body, as will be'readily understood.

Fig. 10 shows a still further modified arrangement for accomplishing the same result. In this case the charging electrode 25 is in the form of a long, narrow metal tube inserted either in or about the pipe line 2 leading from the reservoir 1 to the megaphonefi. In. this arrangement I prefer to put the control electrodes 6 and 7 in the apex of the megaphone or horn 5. In this arrangement, however, I prefer to have the electrodes 6 and 7 of the same polarity and opposite to the polarity of the charging e ectrode 25. If desired, the sub-reservoir 4- may be included between the charging electrode 25 and'the megaphone 5. The electrodes 6 and 7 in this instance are connected together electrically and are connected to one terminal of the secondary 9, of the telephone transformer, and the charging electrode 25 is connected through the current source 14 and 8 to the electrodes 6 and 7. It

through which all the air passing from the reservoir. not shown. tothc horn 5 is-drivcn.

-The metal diaphragm of this acrnngcmcnt constitutes the charging electrode and thus very highly charges the air streams which pass through the finc tubes. whereby the an arriving at the control electrodes 6 and 7 is highly charged and of an opposite potentialto the said electrodes. thc said clm'h'odcs 6 and 7 being connected as in the arrangement The aurus therefore atshown in Fig. 10. tracted to the electrodes 6 and 7 and the normal flow through the space between the electrodes is more or less impeded. Therefore the superimposed impressed alternating E. M. F., which is delivered to'electlodes 35, 6 and 7, will the better interfere with. or

permit, the flow of air through the space separating the electrodes 6 and 7 into'the horn 5, thereby creatin waves in the air emerging from the horn.

I find that a most eflicient and convenient powerful sound way of charging the air as it advances from the reservoir to the control orifice, is by causing the stream of air to pass over an incandescent body which is at the same time highly charged,'preferably with a negative potential. Any suitable incandescent body may be employed. In the arran ement shown in Fig. 12. I employ a Nernst lamp glower illustrated at 45, Fig. 12, which issuitably enclosed in the chamber 4 and heated from a source of current 29 which is connected in series with the customary ballast resistance device 28. This incandescent body is shown connected to the negative end of the charging battery 14 which is in series with the transformer secondary '9 and the control electrodes 6 and 7, located at the orifice leading into the usual horn or megaphone, not shown. In this arrangement. the electrodes 6 and 7 are shown as of the saw-tooth type. Instead of the Nernst lamp glower, I can usea gas flame. the oxygen for which is supplied by means of the air flowing from the reservoir into the chamber containing the gas burner. In this arrangement thegas is burned as in a Bunsen burner, and the air passing over or co-mingled with this flame is heated to a high tempera.- ture and at the same time highly charged negatively. Howevenas there is always more or less noise associated with the operation of such a gas burner prefer to use the Nernst glower heated to incandescence electrically.

Fig. 13 shows a modificationof the above idea in that here the incandescent glower body is located in close proximityio and preferably directly between two cold control electrodes 6 and 7 which are, as I have above described, located at ornear the small orifice of the horn, not shown. Thus the compressed air emerging from the reservoir passing through the narrow space between the Nernst glower 45 and the electrodes 6 and 7 becomes at once ozonized by reason" of passing over the glowing body, negative- 1y charged thereby, and therefore is attracted to the electrodes 6 and 7. Thedegree of this attraction varies, as above de-. scribed, in accordance with the impressed telephonic E. M. F.s, originating or impressed in the secondary coil 9 of the telephone transformer.

Fig. 14 shows the arrangement just described, but with the incandescent glower 45 and the cold electrode 46 (in this case in the form of a metal cylinder surround-- ing the glower), arranged co-axiallyinthe enclosing chamber 4. The air therefore passing through the tube 2 of the horn 5 nust pass through theaiarrow space between. the electrodes 45 and 46. In this arrange'ment I have also shown a grid electrode' 47 in the form of a helix surrounding 95 the incandescent electrode 45 and positioned plibetween the incandescent electrode and the plate electrode. This control electrode is connected to one terminal of the telephone transformer secondary 9, the other terminal of which is connected to one end of the glowe'r 45. The glower is shown connected in series with the source of heating current 29 and the ballast resistance '28. The anode 46 is connected to the positive terminal of a suitable battery or source of E. M. F. 14.

With the arrangement here described, the air passing over the glower becomes ozonized and charged negativelytherefrom. It is therefore attracted to the positively charged electrode 46, but its, transverse passage from 45 to 46 is more or less supereded by the momentary charge impressed upon the grid or control electrode 47. In this way the pulsating potentials impressed between the grid and glower elements are enabledto control the transverse motion of the air particles as they traverse the annular space between the glower and cold anode46, thereby setting up pulsations at a very rapid rate, which pulsations reproduce in the horn 5 the original sound which it is desired to amplify and reproduce. g

In Fig. 15 the air from the reservolr 1, which is insulated from the orifice of the megaphone 5 by means of the insulat ng tube 65, comes out through a narrow annular space in the electrode 6, emerging thus into the center of the horn 5.

Fig. 16 shows the form of the orifice electrode 6. This thin sheet of air"passing'between the fine lips of the annular opening in the electrode 6 is highly charged by virtue of the potential applying to this electrode 6. A metallic disc electrode 66 placed directly around the orifice in the electrode 6, but insulated therefrom by means of suitable annular insulation 68, is .connected to the opposite poleof. the charging source of E. M. F. 8 which is in series also with the secondary of the transformer 910. The sheet of highly charged air emerging from the annular orifice of electrode 6 is therefore i attracted to the oppositely charged electrode 66. When this ditferenceof polarity between the electrodes 6 and 66 is more or lessneutralized by the impressed alternating E. M. F. from the"telephone-coil 9, the sheet of emerging air is moreor less released from the electrode 66, and therefore caused to vibrate somewhat similar to-a metallic diaphragm similarly spaced and charged. The

only vibration that occurs. however, is of the sheet of air'as distinguished from any metallic or mechanical part. Y

Fig. '17'shows a similar arrangement. The air from. reservoir 1 is passed through-tube 2 and. annular tube 62. emerging from all sides over the front face of the disc 66. Directly in front of this diseis placed a grid of fine wires or wire -mesh through the spacesof which the air from 62 emerges into the horn 5. The disc 66 is insulated from the grid or mesh 6 in'the manner illustrated and described with reference to Fig. 15. These two electrodes are connected to the opposite terminals of the transformer coil 9 in series with which may be connected a source of direct current 8. The air thus passing over the surface of the charged disc 66 is electrically charged thereby and therefore strongly attracted to the wires of the oppositely charged mesh 6. In this Way the mesh pliers far greater resistance or impedance to the passage of the charged air there through than would be the case if the disc 66 were charged to a like polarity. Therefore the impedance of this grid or mesh 6 to the passage of the air stream therethrough is controlled by means of the telephonic E. M. F. impressed across the electrodes 6 and 66.

In the arrangement shown in Figs. 18 and 19, the source of compressed air is not shown. In front of the disc electrode and veryclose to, but insulated therefrom, l have shown a grid or mesh 6, the individual wires circlements of which may be insulated by suitable insulation, e. g., enamel or varnish.

All of the elements of the mesh 6 are connected' together as shown in Fig. 19, by means of a common base or supporting member, and this assemblage is connected to one terminal of the transformer secondary 9. The terminal is connected through a suitable source of direct current E. M1 F. to the rear electrode 66. The whole device -is then placed at the small end of the horn 5. By the arrangement here shown, the air in the spacesof the mesh 6 and immediately sur-.,.

thereto, is more or less compressed by virtue of the electrostatic stresses impressed upon this air film. In this way the surrounding air is given alternated impulses pf expansion and compression which produce sound waves in the born 5.

Many other methods and changes in details will readily occur to those skilled in the art without departing from the spirit and scope of my invention as defined in the claims. For example, many other types of forms and locations and means for actuating control and charging electrodes, either or botl1,"willreadily' suggest themselves to those skilled in the art with knowledge ofv the invention here involved. Likew se, many other constructions, types of electrodes,

materials, will readily be apparent to those skilled in the art. It will be-seen, however,

that I have provided a nove l and highly eflicient method .of and means for reproducing sounds by and in accordancewith an electric current, variations of which have been secured by sound waves and whereby diaphragms have been eliminated and all mechanically or electrically moving parts.

I furthermore desire to have the foregoing description and the illustrations employe in conjuction therewith regarded in the illustrative sense and not. in the limiting sense,

comprises passing a fluid under pressure by one or more terminals to which said electric potentials are applied to directly produce sound waves.

2. The method of transforming electric potential variations into sound waves, which. comprises passing air under pressure by one or more terminals to which said electric potentials are applied to directly produce sound waves.

3. The method of transforming electric potential variations into sound waves, which comprises electrifying a fiowingfluid and then passing the same by one or more terminals, to which said electric potentials are applied to produce sound waves.

4:. The method of transforming electric potential variations into sound waves which comprises electrifyin a constantly flowing stream of airand t en passing the same by one or more terminals to which said electric potentials are applied sound waves.

to produce- Ill! 5.' The method of transforming electric potential variations into soundwaves which comprises passing a fluid under pressure bet-ween electrically charged terminals which directly produces sound.

6. The method of transforming electric potential variations into sound'waves, which comprises passing air under pressure between electrically char ed terminals which directly produces soun 7. The method of transforming electric potential variations into sound waves, which comprises electrifying aflowing ,fluid and then passing the-same between electrically charged terminals to produce sound waves.

8. The method of transforming electric potential variations into sound Waves which comprises electrifying a constantly flowing stream of air and then passing the same by one or more terminals to which said electric potentials are applied between electrically charged terminals to produce sound waves.

9. The method of transforming electric potential variations into sound waves, which comprises passing a fluid under pressure over one or more highly charged terminals, and then passing the same by one or more terminals to which said electric potentials are applied to produce sound waves.

10. The method of transforming electric potential'variations into sound waves, which comprises passing air under pressure over one or more highly charged terminals, and then passing the same by one or more terminals to which said electric potentials are applied to produce sound waves.

11. The method of transforming electric potential variations into sound waves which comprises passing a fluid under pressure over one or more highly charged terminal and then passing the same between separated terminals to which said potentials are applied to produce sound waves.

12. The method of transforming electric potential variations into sound waves, which comprises passing air under pressure over one or more highly char ed terminals, and then passing the same lietween separated terminals to which said potentials are applied to produce sound waves.

- 13. The method of transforming electric potential variations into sound waves, which comprises passing a fluidunder pressure by an electrically heated body and then by one or more terminals to which said potentials are applied to produce sound waves.

14. The method of transformingselectric potential variations into sound waves, which comprises. passing a column of air by an electrically heated body and then by one or more terminals to which said potentialsare applied to produce sound waves.

15. The method of transforming electric potential variations into sound waves which comprises passing a fluid by a plurality of separated terminals, one of which is heated,

and the others having said potential variations applied thereto to produce sound waves.

16. The methodmf transforming electric potential variations into sound waves which comprises passing a column of air by a plurality of terminals, one of which is heated, and the others having said potential variations applied thereto to produce sound waves.

17. Means for transforming telephonic potential variations into sound waves comprising a source of fluid pressure, an outlet therefor, an electrode positioned in the path of said fluid pressure, and means for applying. said potential variations to said electrode to produce sound waves. 18. llll-cans for transforming telephonic potential variations into sound waves comprising a source of fluid pressure, an outlet therefor, a plurality of electrodes positioned in the path of said fluid pressure, and means for applying said potential variations to said electrodes.

19. Means for transforming telephonic potential variations into sound waves coinprising' a source of fluid pressure, an outlet therefor, means for electrifying said fluid pressure, and means for applying said potential variations to said electrified fluid pressure.

20. Means for transforming telephonic potential variations into sound waves comprising a source of fluid pressure, an outlet therefor, and means for applying said potential variations to said fluid pressure.

Intestimony whereof I have hereunto set my hand on this 25th day of April, A. D.

LEE on FOREST. 

